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The prerequisites for running the package are outlined in the LEXT Installation Manual. Assuming everything is correctly set up, the package is invoked from DCL by typing:
$ LEXTThe startup file is executed (see section 9.8 for description) and several status messages are written to the screen. The main prompt then appears:
LEXT - IMAGE 1 >
LEXT is command language driven, with a fairly sophisticated interpreter. The LEXT commands themselves, summarised in appendix A, have the familiar DCL format of verb (or command), nouns (or parameters), and adverbs (or qualifiers). The interpreter normally accepts the minimum unambiguous shortening for commands and qualifiers.
If the necessary information is not supplied on the command line then it is prompted for through the parameter system. When prompted the user can either supply the parameter value, or, if a default is offered, press Return to accept this . Alternatively the user can type ? to get a brief help description of the input required, or type ! or !! to exit the routine back to the command line. Some routines, which are likely to be a long time in execution, and which are reporting to the terminal, may be aborted using Ctrl-C, which should be trapped and returning you to the command line. This does not apply to, for example, graphical displaying.
The parameters are frequently slots which are the internal data storage objects, as described in section 9. Slots are referenced by their number rather than the name of the object they contain. The command prompt includes the number of the slot currently in use and the current mode.
Most operations, by default, use the current slot as the source and the first free slot as destination. Some operations are specific to either list or image, whilst others may apply to both (eg. COPY).